Plans:•Read About False Memories (Beth Loftus) for Thursday (April 7th)

•Read About Amnesia (Oliver Sacks) for Tuesday (April 12th)

•Read about Subliminal Messages (Vokey and Reed) for Thursday (April 14th)

Memory

Short-Term “Working” Memory

Overview of Memory

• Atkinson-Shiffrin Model

Sensory Signals

Sensory Memory

Short-Term Memory

Long-Term Memory

ATTENTION

REHEARSAL

RETRIEVAL

Short-Term Memory

• process by which we hold information “in mind”

Short-Term Memory

• process by which we hold information “in mind”

• example: temporarily remembering a phone number

Characteristics of STM

• Duration? Capacity?

• How could one measure these parameters?

Characteristics of STM

• Limited Duration– Brown-Petersen Task:

• subject is given a trigram (e.g. C-F-W) to remember

• vocal rehearsal is prevented by counting backwards

• recall accuracy tested as a function of retention interval

Characteristics of STM

• STM decays over seconds

Characteristics of STM

• Limited Duration– Brown-Petersen Task Interpretation: rapid

loss of information in STM (over a period of seconds…much longer than sensory memory)

Characteristics of STM

• Limited Capacity– How might you measure capacity?

Characteristics of STM

• Limited Capacity– George Miller – Subject is given longer and longer lists of to-

be-remembered items (words, characters, digits)

Characteristics of STM

• Limited Capacity– George Miller – Subject is given longer and longer lists of to-

be-remembered items (words, characters, digits)

– Result: Subjects are successful up to about 7 items

Characteristics of STM

• Limited Capacity– What confound must be considered ?!

Characteristics of STM

• Limited Capacity– What confound must be considered ?!– Recalling takes time !

Characteristics of STM

• Limited Capacity– What confound must be considered ?!– Recalling takes time !– It seems that the “capacity” of STM (at least

measured in this way) depends on the rate of speech - faster speech leads to apparently larger capacity

– Some believe capacity is “2 - 3 seconds worth of speech”

Forgetting from STM

• Why do we “forget” from STM?– Does the memory trace decay?

• not likely because with very small lists (like 1 item) retention is high for long intervals

Forgetting from STM

• Why do we “forget” from STM?– Does the memory trace decay?

• not likely because with very small lists (like 1 item) retention is high for long intervals

– Instead, it seems that information “piles up” and begins to interfere

Forgetting from STM

• Interference in STM is complex and specific

Forgetting from STM

• Interference in STM is complex and specific

• For example, severity of interference depends on meaning

Forgetting from STM

• Interference in STM is complex and specific

• For example, severity of interference depends on meaning– Subjects are given successive recall tasks with

list items from the same category (e.g. fruits)– final list is of either same or different category -

how is good is recall on this list?

Forgetting from STM

• Accuracy rebounds if category changes

Coding in STM

• How is information coded in STM?

Coding in STM

• Clues about coding in STM:– # of items stored in STM depends on rate of speech

Coding in STM

• Clues about coding in STM:– # of items stored in STM depends on rate of speech– phonological similarity effect: similar sounding words are harder to store/recall than different

sounding words

Coding in STM

• Clues about coding in STM:– # of items stored in STM depends on rate of speech– phonological similarity effect: similar sounding words are harder to store/recall than different

sounding words

What does this suggest about the nature of information in STM?

Coding in STM

• It seems that information can be stored in a linguistic or phonological form

Coding in STM

• It seems that information can be stored in a linguistic or phonological form

Must it be stored this way?

Coding in STM

• It is also possible to “keep in mind” non-verbal information, such as a map

Are there two different STM systems?

A Modular Approach to STM

• Allan Baddeley:

Articulatory Loop

Central Executive

Visuospatial Sketchpad

In general, how can we know if there are one, two, or more independent systems handling

some aspect of perception or cognition?

A Modular Approach to STM

• Double-Dissociation: Indicates that two processes or systems are independent

A Modular Approach to STM

• A dissociation occurs when one process is influenced by changing a variable but another process is not

A Modular Approach to STM

• A dissociation occurs when one process is influenced by changing a variable but another process is not

• A double-dissociation occurs when two different processes are influenced by changing two different variables

A Modular Approach to STM

Performance

Damage

Sparkplugs

Engine

Radio

Antenna

A Modular Approach to STM

• The logic of double-dissociation informs us about working memory modules

A Modular Approach to STM

Articulatory Loop

Central Executive

Visuospatial Sketchpad

Experiment 1 in the article by Lee Brooks demonstrates a double dissociation between Articulatory Loop and Visuospatial Sketchpad

Working Memory “Modules”

• Lee Brooks: interference between different representations in STM (Experiment 1)– Memory Representation

• verbal task: categorize words in a sentence

• spatial task: categorize corners in a block letter

– Response Modality• verbal response: say “yes” or “no”

• spatial response: point to “yes” or “no”

Working Memory “Modules”

• result:

Per

form

ance

Response Modality

Verbal Spatial

Spatial Representation(categorize corners)

Verbal Representation(categorize words)

Working Memory “Modules”

• Interpretation:– supports notion of modularity in Working Memory (visuospatial sketchpad / articulatory loop)

Next Time:

• Long-Term Memory• Read Loftus for Next Thursday